Chip sealing is a cost effective surface treatment used on about one quarter of Seattle’s non-arterial streets.

A chip seal surface consists of an application of asphalt emulsion and a layer of “rock chips” which are about 1/4 to 3/8 of an inch wide. Chip sealing is a commonly used preventive maintenance activity for non-arterial streets in many cities and counties.

Why are some streets chip sealed?

In the 1960’s, most of these streets were dirt or gravel. The City converted them to chip seal to provide a smooth driving surface, reduce dust and improve air quality.

Our street looks fine—why reseal it?

Chip sealed streets need periodic resealing to protect them from the deteriorating effects of water (rain) and sun. If left untreated, the surface becomes brittle and may crack. Periodic resealing will prevent more extensive and costly repairs. Regular preventive maintenance is the most cost effective way to maintain streets.

2013 Project

One chip seal project is funded for 2013. The project is in the Crown Hill / Greenwood neighborhood. This project area is roughly bounded by N/NW 110th Street to the north, N/NW 85th Street to the south, 15th Avenue to the west, and Greenwood Avenue N to the east. Most of the streets in this area will be chip sealed. Click here to view the map of streets to be chip sealed in 2013.

Background

Preparation

It is essential that damage to the road, such as potholes and cracks, be repaired prior to the chip seal process. SDOT crews will begin to patch deteriorated areas of the selected roads in the spring, well in advance of the chip seal operation.

In addition, low hanging branches and overgrowth may need to be trimmed to allow for the chip seal equipment to navigate the roads.

The Chip Seal Process

First, an asphalt emulsion is applied to the street surface and is immediately followed by a computer-operated chip spreader which evenly spreads rock chips onto the emulsion. The rock is then embedded in the emulsion by rollers.
At this point, the road is ready for use.

Unlike asphalt or concrete streets, chip sealed streets can be driven on almost immediately after the surface is applied. However, we do ask that for the first few days, cars drive no more than 10 miles per hour over the new surface. This will allow the rocks to set and reduce the chance of loose rock damage to your vehicle.

This work typically happens in the middle of the summer (July), when it is warm and there is little chance of rain.

After the chip seal operation is complete, SDOT will sweep the streets to remove loose rock chips.

Factoids

Chip sealing is a cost-efficient surface treatment that lasts about 10 years, where traffic volumes are low and not used by heavy trucks or buses.

The crews can cover up to three to four miles a day.

The City of Seattle began converting dirt and gravel non-arterial streets to chip seal in 1967 with federal money available for this purpose. The goal was to reduce the release of dust and other pollutants into the air and improve air quality. Later, chip seal streets were maintained with local funds.

Tips for Residents during Chip Seal Projects

Parking

Parking will be restricted on the streets that will be chip sealed. “No Parking” signs will be placed along both sides of the streets prior to the work so you can move your car from the street or shoulder. Parking restrictions are typically removed as soon as we’re done with the chip seal application. The application process is done within a day.

Traffic Access

Access to your driveway may be disrupted for a few minutes, but SDOT crews will work to minimize any delays. The new surface can be driven on almost immediately, but slow speeds are required.

Sweeping

We expect some loose rock after the chip sealing. SDOT’s mechanical sweepers will sweep the streets within several days to remove excess loose rock. The roadway surface will improve over several weeks as the surface stabilizes, resulting in a stronger more durable street.

Drive Slowly

Please drive slowly, no faster than 10 mph, on the new surface for the first several days. This will help the new surface to set and prevent the loosening of aggregate.

Motorcyclists and Bicyclists

Due to the loose rock, motorcyclists and bicyclists should use extreme caution and consider using alternative routes until the road surface stabilizes.

Pets

To avoid contact with the asphalt emulsion on the street, please keep pets indoors or fenced-in during the day of the chip seal project.